Skip to main content
Chemistry LibreTexts


  • Page ID
  • \( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)

    \( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)

    \( \newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\)

    ( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\)

    \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\)

    \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\)

    \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\)

    \( \newcommand{\Span}{\mathrm{span}}\)

    \( \newcommand{\id}{\mathrm{id}}\)

    \( \newcommand{\Span}{\mathrm{span}}\)

    \( \newcommand{\kernel}{\mathrm{null}\,}\)

    \( \newcommand{\range}{\mathrm{range}\,}\)

    \( \newcommand{\RealPart}{\mathrm{Re}}\)

    \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\)

    \( \newcommand{\Argument}{\mathrm{Arg}}\)

    \( \newcommand{\norm}[1]{\| #1 \|}\)

    \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\)

    \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\AA}{\unicode[.8,0]{x212B}}\)

    \( \newcommand{\vectorA}[1]{\vec{#1}}      % arrow\)

    \( \newcommand{\vectorAt}[1]{\vec{\text{#1}}}      % arrow\)

    \( \newcommand{\vectorB}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)

    \( \newcommand{\vectorC}[1]{\textbf{#1}} \)

    \( \newcommand{\vectorD}[1]{\overrightarrow{#1}} \)

    \( \newcommand{\vectorDt}[1]{\overrightarrow{\text{#1}}} \)

    \( \newcommand{\vectE}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash{\mathbf {#1}}}} \)

    \( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)

    \( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)

    \(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)
     Example and Directions
    Words (or words that have the same definition) The definition is case sensitive (Optional) Image to display with the definition [Not displayed in Glossary, only in pop-up on pages] (Optional) Caption for Image (Optional) External or Internal Link (Optional) Source for Definition
    (Eg. "Genetic, Hereditary, DNA ...") (Eg. "Relating to genes or heredity") Green DNA strand cartoon. The infamous double helix Biology, Libretexts CC-BY-SA; Delmar Larsen
    Glossary Entries
    Word(s) Definition Image Caption Link Source
    Acetyl-CoA A molecule that participates in many biochemical reactions in protein, carbohydrate and lipid metabolism. Its main function is to deliver the acetyl group to the citric acid cycle (Krebs cycle) to be oxidized for energy production.        
    addition polymerization A reaction in which monomers add to one another to produce a polymeric product that contains all the atoms of the starting monomers.        
    addition reactions A reaction in which substituent groups join to hydrocarbon molecules at points of unsaturation—the double or triple bonds.        
    alcohol An organic compound with an OH functional group on an aliphatic carbon atom.        
    aldehyde An organic compound with a carbonyl functional group that has an hydrogen atom attached and either a hydrocarbon group or a second hydrogen atom.        
    alkaloid A nitrogen-containing organic compound obtained from plants that has physiological properties.        
    alkanes (or saturated hydrocarbons) A hydrocarbon with only carbon-to-carbon single bonds and existing as a continuous chain of carbon atoms also bonded to hydrogen atoms        
    alkenes A hydrocarbon with one or more carbon–carbon double bonds.        
    alkyl group A hydrocarbon group derived from an alkane by removal of a hydrogen atom.        
    alkyl halide (or haloalkane) A compound resulting from the replacement of a hydrogen atom of an alkane with a halogen atom.        
    Alkynes A hydrocarbon with a carbon–carbon triple bond.        
    alloy A solid solution of a metal with other substances dissolved in it.        
    alpha particle A type of radioactive emission that is equivalent to a helium atom nucleus.        
    amide An organic compound with a carbonyl group joined to a nitrogen atom from ammonia or an amine.        
    amine An organic compound derived from ammonia by the replacement of one, two, or three of the hydrogens atoms by alkyl or aryl groups.        
    amino group An NH2 unit.        
    amorphous A solid with no regular structure.        
    amphiprotic A substance that can either donate or accept a proton, depending on the circumstances.        
    amylopectin A branched polymer of glucose units found in starch.        
    anabolism Metabolic reactions in which molecules are synthesized.        
    anaerobic metabolism A biochemical process that takes place in the absence of oxygen.        
    anions A negatively charged ion.        
    anomeric carbon The carbon atom that was the carbonyl carbon atom in the straight-chain form of a monosaccharide.        
    anticodon A set of three nucleotides on the tRNA that is complementary to, and pairs with, the codon on the mRNA.        
    antioxidants A substance in foods that acts as a reducing agent.        
    aromatic compound Any compound that contains a benzene ring or has certain benzene-like properties.        
    aromatic hydrocarbons A hydrocarbon with a benzene-like structure.        
    aryl group A group derived from an aromatic hydrocarbon by the removal of a hydrogen atom.        
    atomic bomb A weapon that depends on a nuclear chain reaction to generate immense forces.        
    atomic mass A weighted average of the masses of all the element’s naturally occurring isotopes.        
    atomic mass unit One-twelfth the mass of a 12C atom.        
    atomic radius The approximate size of an atom.        
    autoionization of water The process by which water ionizes into hydronium ions and hydroxide ions as it acts as an acid and a base.        
    Avogadro’s number The value 6.022 × 1023.        
    balanced A property of a chemical equation when there are the same number of atoms of each element in the reactants and products.        
    base A compound that increases the concentration of hydroxide ion (OH) in aqueous solution.        
    Base (or basic) units A fundamental unit of SI.        
    beta particle A type of radioactive emission that is equivalent to an electron.        
    Bilayers A double layer of lipids arranged so that nonpolar tails are found between an inner surface and outer surface consisting of hydrophilic heads.        
    Bile The yellowish green liquid produced in the liver.        
    biochemistry The chemistry of molecules found in living organisms.        
    boiling point The temperature at which a substance goes from a liquid to a gas (or from a gas to a liquid).        
    boiling point elevation The raising of the boiling point of a solution versus the pure solvent.        
    bond length The distance between two nuclei in a covalent bond.        
    Boyle’s law The gas law that relates pressure and volume.        
    Brønsted-Lowry base A compound that accepts a hydrogen ion (H+) in a reaction; a proton acceptor.        
    buffer A solution that resists dramatic changes in pH.        
    calorie A unit of energy widely used in the health professions and everyday life.        
    capacity The amount of strong acid or base a buffer can counteract.        
    carbohydrates A compound composed of carbon, hydrogen, and oxygen atoms that is a polyhydroxy aldehyde or ketone or a compound that can be broken down to form such a compound. It is one of the three main components of the human diet.        
    carboxyl group A functional group that contains a carbon–oxygen bond and an OH group also attached to the same carbon atom.        
    carboxylic acids An organic compound that has a carboxyl functional group.        
    cations A positively charged ion.        
    cerebrosides A sphingolipid that contains a fatty acid unit, a sphingosine unit, and galactose or glucose.        
    chain reaction An exponential growth in a process.        
    Charles’s law The gas law that relates volume and absolute temperature.        
    chemical bond A very strong attraction between two atoms.        
    chemical equilibrium (or equilibrium) The condition in which the extent of a chemical reaction does not change any further.        
    chemical formula A concise list of the elements in a compound and the ratios of these elements.        
    Chemical properties A characteristic that describes how matter changes its chemical structure or composition.        
    chemical reaction A representation of a chemical change.        
    chemical symbol A one- or two-letter abbreviation for an element.        
    chiral carbon A carbon atom that has four different groups attached to it.        
    Cholesterol A steroid that is found in mammals.        
    cis-trans isomers (or geometric isomers) Isomers that have different configurations because of the presence of a rigid structure such as a double bond or ring.        
    citric acid cycle, Krebs cycle, tricarboxylic acid  cycle, TCA cycle A cyclic sequence of reactions that brings about the oxidation of a two-C unit to carbon dioxide and water.        
    codon A set of three nucleotides on the mRNA that specifies a particular amino acid.        
    coefficient A number that gives the number of molecules of a substance in a balanced chemical equation.        
    coenzymes A cofactor that is an organic molecule.        
    colligative properties A characteristic of solutions that depends only on the number of dissolved particles.        
    combination (composition) reaction A chemical reaction that makes a single substance from two or more reactants.        
    combined gas law The gas law that relates pressure, volume, and absolute temperature.        
    combustion reaction A chemical reaction in which a substance combines with molecular oxygen to make oxygen-containing compounds of other elements in the reaction.        
    competitive inhibitor A compound that resembles a particular substrate and competes with the substrate for binding at the active site of an enzyme to slow the rate of the reaction.        
    complementary bases Specific base pairings in the DNA double helix.        
    compound A substance that can be broken down into chemically simpler components.        
    concentration How much solute is dissolved in a certain amount of solvent.        
    condensed structural formulas An organic chemical formula that shows the hydrogen atoms (or other atoms or groups) right next to the carbon atoms to which they are attached.        
    conversion factor A fraction that has equivalent quantities in the numerator and the denominator but expressed in different units.        
    core electrons An electron in a lower-numbered shell of an atom.        
    covalent network bonding A type of interaction in which all the atoms in a sample are covalently bonded to other atoms.        
    curie (Ci) A unit of radioactivity equal to 3.7 × 1010 decays per second.        
    cyclic hydrocarbons A hydrocarbon with a ring of carbon atoms.        
    cycloalkanes A cyclic hydrocarbon with only single bonds.        
    cytochromes A protein that contains an iron porphyrin in which iron can alternate between Fe(II) and Fe(III).        
    cytoplasm Everything between the cell membrane and the nuclear membrane.        
    decomposition reaction A chemical reaction in which a single substance is converted into two or more products.        
    Denaturation Any change in the three-dimensional structure of a macromolecule that renders it incapable of performing its assigned function.        
    Density The mass of an object divided by its volume.        
    Derived units A combinations of the SI base units.        
    diatomic molecules A two-atom grouping that behaves as a single chemical entity.        
    digestion The breakdown of food molecules by hydrolysis reactions into the individual monomer units in the mouth, stomach, and small intestine.        
    dipole-dipole interaction An attraction between polar molecules.        
    Dispersion forces A force caused by the instantaneous imbalance of electrons about a molecule.        
    dispersion forces (or London forces) A force caused by the instantaneous imbalance of electrons about a molecule.        
    dissociation The process of cations and anions of an ionic solute separating when the solute dissolves.        
    Disulfide linkages A covalent bond that forms by the oxidation and linkage of two sulfur atoms from the side chains of two cysteine residues.        
    double bond Two pairs of electrons being shared by two atoms in a molecule.        
    electron A subatomic particle with a negative electric charge.        
    electron configuration A shorthand description of the arrangement of electrons in an atom.        
    electron transport chain (or respiratory chain) An organized sequence of oxidation-reduction reactions that ultimately transports electrons to oxygen, reducing it to water.        
    electronegativity A relative measure of how strongly an atom attracts electrons when it forms a covalent bond.        
    emulsion A dispersion of two liquids that do not normally mix.        
    enantiomers Stereoisomers that are nonsuperimposable mirror images of each other.        
    endothermic A process that absorbs energy.        
    Energy The ability to do work.        
    equivalents (Eq) One mole of charge (either positive or negative).        
    essential fatty acids A fatty acid that must be obtained from the diet because it cannot be synthesized by the human body.        
    ester An organic compound derived from a carboxylic acid and an alcohol in which the OH of the acid is replaced by an OR group.        
    esterification The formation of an ester from a carboxylic acid and an alcohol.        
    ether An organic compound that has an oxygen atom between two hydrocarbon groups.        
    Exact numbers A number that is defined or counted.        
    exothermic A process that gives off energy.        
    fats A compound, composed largely of hydrocarbon chains, that supplies energy for the body.        
    Feedback inhibition A normal biochemical process that makes use of noncompetitive inhibitors to control some enzymatic activity.        
    fibrous proteins A protein that is elongated or fiberlike and insoluble in water.        
    formula mass The sum of the masses of the elements in the formula of an ionic compound.        
    formula unit A set of oppositely charged ions that compose an ionic compound.        
    freezing point depression The lowering of the freezing point of a solution versus the pure solvent.        
    functional group, functional groups A structural arrangement of atoms and/or bonds that imparts a wide range of important properties to organic compounds.        
    Fusion A nuclear process in which small nuclei are combined into larger nuclei, releasing energy.        
    galactosemia A genetic disease caused by the absence of one of the enzymes needed to convert galactose to glucose.        
    gamma rays A type of radioactive emission that is a very energetic form of electromagnetic radiation.        
    gangliosides A sphingolipid that contains a fatty acid unit, a sphingosine unit, and a complex oligosaccharide.        
    gas law A simple mathematical formula that relates two or more properties of a gas.        
    Gastric juice A mixture of water, inorganic ions, hydrochloric acid, and various enzymes and proteins found in the stomach.        
    Geiger counter An electrical device that detects radioactivity.        
    genes The basic unit of heredity.        
    genetic code The identification of each group of three nucleotides and its particular amino acid.        
    genetic diseases A hereditary condition caused by an altered DNA sequence.        
    Globular proteins A protein that is generally spherical in structure and soluble in water.        
    glycols An alcohol with two OH functional groups.        
    glycolysis The metabolic pathway in which glucose is broken down to two molecules of pyruvate with the corresponding production of ATP.        
    glycosidic linkage The carbon–oxygen-carbon linkage between monosaccharide units in more complex carbohydrates, such as disaccharides or polysaccharides.        
    groups (or families) A column of elements on the periodic table.        
    half reactions A chemical reaction that shows only oxidation or reduction.        
    half-life The amount of time it takes for one-half of a radioactive isotope to decay.        
    halogenated hydrocarbons A hydrocarbon in which one or more hydrogen atoms has been replaced by a halogen atom.        
    halogenation A reaction in which a halogen reacts at a carbon-to-carbon double or triple bond to add halogen atoms to carbon atoms.        
    heat The transfer of energy from one part of the universe to another due to temperature differences.        
    heat of vaporization The amount of heat per gram or per mole required for a phase change that occurs at the boiling point.        
    heterocyclic compounds A cyclic compound in which one or more atoms in the ring is an element other than a carbon atom.        
    homogeneous mixtures, homogeneous mixture, homogeneous solution A mixture that acts as a single substance so that it is not obvious that two or more substances are present.        
    homologous series Any family of compounds in which adjacent members differ from each other by a definite factor.        
    hydration Solvation by water molecules.        
    Hydrogen bonding Bonding between a highly electronegative oxygen atom or nitrogen atom and a hydrogen atom attached to another oxygen atom or nitrogen atom.        
    hydrogenation A reaction in which hydrogen gas reacts at a carbon-to-carbon double or triple bond or a carbon-to-oxygen double bond to add hydrogen atoms to carbon atoms.        
    hydrolysis The reaction of a substance with water.        
    ideal gas law The gas law that relates volume, pressure, temperature, and amount of a gas.        
    ideal gas law constant The constant the appears in the ideal gas law.        
    immiscible Liquids that do not dissolve in each other.        
    induced-fit model A model that says an enzyme can undergo a conformational change when it binds substrate molecules.        
    inner transition metals An element in the two rows beneath the main body on the periodic table. Such metals are also called the lanthanide and actinide elements.        
    inorganic chemistry The study of the chemistry of all other elements.        
    intermolecular interactions A force of attraction between different molecules.        
    Ionic bonding Bonding that results from electrostatic attractions between positively and negatively charged groups.        
    ionic compounds A compound formed with an ionic bond.        
    ionic interactions An attraction due to ions of opposite charges.        
    irreversible inhibitor A substance that inactivates an enzyme by bonding covalently to a specific group at the active site.        
    isoelectric point The pH at which a given amino acid exists in solution as a zwitterion.        
    isomers Compounds having the same molecular formula but different structural formulas and properties.        
    isothermal A process that occurs at constant temperature.        
    isotopes Atoms of the same element that have different numbers of neutrons.        
    IUPAC System of Nomenclature A systematic way of naming chemical substances so that each has a unique name.        
    joule The SI unit of energy, work, and heat.        
    ketogenic amino acids An amino acid that is converted to acetoacetyl-CoA or acetyl-CoA, which can be used for the synthesis of ketone bodies but not glucose.        
    ketone An organic compound whose molecules have a carbonyl functional group between two hydrocarbon groups.        
    ketoses A monosaccharide that contains a ketone functional group on the second carbon atom.        
    kinetic theory of gases The fundamental theory of the behavior of gases.        
    L sugars A sugar whose Fischer projection terminates in the same configuration as L-glyceraldehyde.        
    lattice energy The strength of interactions between atoms that make ionic bonds.        
    law A general statement that explains a large number of observations.        
    law of conservation of matter In any given system that is closed to the transfer of matter (in and out), the amount of matter in the system stays constant.        
    Lewis diagrams A representation that shows valence electrons as dots around the chemical symbol of an atom (also called Lewis electron dot diagrams).        
    line-angle formula An organic chemical formula in which carbon atoms are implied at the corners and ends of lines. Each carbon atom is understood to be attached to enough hydrogen atoms to give each carbon atom four bonds.        
    lipids A compound isolated from body tissues that is more soluble in organic solvents than in water.        
    lock-and-key model A model that portrays an enzyme as conformationally rigid and able to bond only to a substrate or substrates that exactly fit the active site.        
    mass number The sum of the numbers of protons and neutrons in a nucleus of an atom.        
    mass-mass calculations A stoichiometry calculation converting between the mass of one substance and the mass of a different substance in a chemical reaction.        
    mass/mass percent A concentration unit that relates the mass of the solute to the mass of the solution.        
    mass/volume percent A concentration unit that relates the mass of the solute to the volume of the solution.        
    Matter Anything that has mass and takes up space.        
    metabolic pathway A series of biochemical reactions by which an organism converts a given reactant to a specific end product.        
    microscopic A view of the universe in which one is working with a few atoms or molecules at a time.        
    mitochondria Small, oval organelles with double membranes; the “power plants” of a cell.        
    modern atomic theory The fundamental concept that all elements are composed of atoms.        
    molar mass The mass of 1 mol of atoms or molecules.        
    Molarity Number of moles of solute per liter of solution.        
    mole-mass calculations A stoichiometry calculation converting between masses and moles of different substances in a chemical reaction.        
    mole-mass conversion The conversion from moles of material to the mass of that same material.        
    molecular formulas A chemical formula for a covalent compound.        
    molecular mass The mass of a molecule, which is the sum of the masses of its atoms.        
    molecule A discrete group of atoms connected by covalent bonds.        
    mutagens A chemical or physical agent that cause mutations.        
    mutarotation The ongoing interconversion between anomeric forms of a monosaccharide to form an equilibrium mixture.        
    mutation Any chemical or physical change that alters the nucleotide sequence in DNA.        
    neutralization The reaction of acid and base to make water and a salt.        
    neutron A subatomic particle with no electric charge.        
    nomenclature The systematic naming of chemical compounds.        
    nonbonding pairs (or lone pairs) Electron pair that does not participate in covalent bonds.        
    noncompetitive inhibitor A compound that can combine with either the free enzyme or the enzyme-substrate complex at a site distinct from the active site to slow the rate of the reaction.        
    nonelectrolytes A compound that does not ionize at all when it dissolves.        
    nonpolar covalent bond A covalent bond with a balanced electron distribution across the bond.        
    Nuclear energy The controlled harvesting of energy from fission reactions.        
    nuclear reactor An apparatus designed to carefully control the progress of a nuclear reaction and extract the resulting energy for useful purposes.        
    nucleotides A monomer unit that is linked together to form nucleic acids.        
    nucleus The central part of an atom that contains protons and neutrons.        
    octet rule The idea that atoms tend to have eight electrons in their valence shell.        
    oil A triglyceride that is a liquid at room temperature.        
    optimum pH The pH at which a particular enzyme exhibits maximum activity.        
    Organic chemistry The study of the chemistry of carbon compounds.        
    organic compound A compound containing carbon atoms.        
    Osmolarity A way of reporting the total number of particles in a solution to determine the osmotic pressure.        
    osmotic pressure The tendency for solvent molecules to move from the more dilute solution to the more concentrated solution until the concentrations of the two solutions are equal.        
    oxidative deamination A reaction in which glutamate loses its amino group as an ammonium ion and is oxidized back to α-ketoglutarate.        
    oxidative phosphorylation The process that links ATP synthesis to the operation of the electron transport chain.        
    oxidizing agent A species that causes oxidation, which is itself reduced.        
    parts per billion (ppb) The mass of a solute compared to the mass of a solution times 1,000,000,000.        
    peptide bond The amide bond joining two amino acid units in a peptide or protein.        
    period A row of elements on the periodic table.        
    periodic table A chart of elements that groups the elements by some of their properties.        
    peripheral proteins A protein that is more loosely associated with the membrane surface.        
    pH scale A logarithmic scale that relates the concentration of the hydrogen ion in solution.        
    phase A form of matter that has the same physical properties throughout.        
    phase change A physical process in which a substance goes from one phase to another.        
    phases A certain form of matter that includes a specific set of physical properties.        
    phenols An aromatic compound with an OH group attached directly to a benzene ring.        
    photosynthesis The process by which plants use solar energy to convert carbon dioxide and water to glucose.        
    point mutations A change in which one nucleotide is substituted, added, or deleted.        
    polar A molecule with a net unequal distribution of electrons in its covalent bonds.        
    polyamide A condensation polymer in which the monomer units are joined by an amide linkage.        
    polyatomic ions An ion with more than one atom.        
    polycyclic aromatic hydrocarbons (PAHs) An aromatic hydrocarbon consisting of fused benzene rings sharing a common side.        
    polymers A giant molecule formed by the combination of monomers in a repeating manner.        
    polypeptides A chain of about 50 or more amino acids.        
    polysaccharides A carbohydrate containing many monosaccharide units.        
    polyunsaturated fatty acids A fatty acid that has two or more carbon-to-carbon double bonds.        
    power The exponent in a number expressed in scientific notation.        
    pressure Force divided by area.        
    primary (1°) alcohol A compound with an OH group on a carbonatom that is attached to only one other carbon atom.        
    primary structure The sequence of amino acids in a polypeptide chain or protein.        
    products A substance on the right side of the arrow in a chemical equation.        
    Proteins A compound of high molar mass consisting largely or entirely of amino acids linked together.        
    proton A subatomic particle with a positive charge.        
    purines A heterocyclic amine consisting of a pyrimidine ring fused to a five-member ring with two nitrogen atoms.        
    quantized Having a fixed value.        
    quantum mechanics The modern theory of electron behavior.        
    quaternary structure The arrangement of multiple subunits in a protein.        
    rad A unit of radioactive exposure equal to 0.01 J/g of tissue.        
    radioactivity Emanations of particles and radiation from atomic nuclei.        
    reducing sugar Any carbohydrate capable of reducing a mild oxidizing agent, such as Tollens’ or Benedict’s reagents, without first undergoing hydrolysis.        
    rem A unit of radioactive exposure that includes a factor to account for the type of radioactivity.        
    replication The process in which the DNA in a dividing cell is copied.        
    respiration The process by which cells oxidize organic molecules in the presence of gaseous oxygen to produce carbon dioxide, water, and energy in the form of ATP.        
    retroviruses An RNA virus that directs the synthesis of a DNA copy in the host cell.        
    ribonucleic acid, RNA The nucleic acid responsible for using the genetic information encoded in DNA.        
    ribosomes A cellular substructure where proteins are synthesized.        
    round The process of assessing the final significant figure of a quantity to determine if it should be kept or moved higher.        
    saponification The hydrolysis of fats and oils in the presence of a base to make soap.        
    science The process by which we learn about the natural universe by observing, testing, and then generating models that explain our observations.        
    scientific method An organized procedure for learning answers to questions.        
    secondary (2°) alcohol A compound with an OH group on a carbon atom that is attached to two other carbon atoms.        
    secondary structure The fixed arrangement of the polypeptide backbone.        
    semimetals, metalloids An element whose properties are intermediate between metals and nonmetals.        
    shells A grouping of electrons within an atom.        
    significant figures All the digits of a measured quantity known with certainty and the first uncertain, or estimated, digit.        
    single bond A covalent bond formed by a single pair of electrons.        
    solubility The limit of how much solute can be dissolved in a given amount of solvent.        
    solute The minor component of a solution.        
    solution Another name for a homogeneous mixture.        
    specific heat A proportionality constant that relates heat to a temperature change.        
    Sphingolipids A lipid that contains the unsaturated amino alcohol sphingosine.        
    Sphingomyelins A sphingolipid that contains a fatty acid unit, a phosphoric acid unit, a sphingosine unit, and a choline unit.        
    spontaneous fission, fission The breaking apart of an atomic nucleus into smaller nuclei.        
    standard temperature and pressure, STP 273 K (0°C) and 1.00 atm pressure.        
    steroids A lipid with a four-fused-ring structure.        
    Stock system The system of indicating a cation’s charge with roman numerals.        
    stoichiometry The study of the numerical relationships between the reactants and the products in a balanced chemical equation.        
    strong acid An acid that is 100% ionized in aqueous solution.        
    strong base A base that is 100% ionized in aqueous solution.        
    structural formula A chemical formula that shows how the atoms of a molecule are attached to one another.        
    subshells A grouping of electrons within a shell.        
    substrate-level phosphorylation The synthesis of ATP by the direct transfer of a phosphate group from a metabolite to ADP.        
    substrates A compound on which an enzyme acts.        
    tertiary (3°) alcohol A compound with an OH group on a carbon atom that is attached to three other carbon atoms.        
    tertiary (3°) amine A compound that has three alkyl or aryl groups on the nitrogen atom.        
    tertiary structure The unique three-dimensional shape of a polypeptide chain as a whole.        
    theory A general statement that describes a large set of observations and data.        
    Thiols A compound with an SH functional group.        
    torr Another name for millimeters of mercury.        
    tracer A substance that can be used to follow the pathway of that substance through some structure.        
    transamination An exchange of functional groups between any amino acid and an α-keto acid.        
    transcription The process in which RNA is synthesized from a DNA template.        
    translation The process in which the information encoded in mRNA is used to direct the sequencing of amino acids to synthesize a protein.        
    triglycerides An ester composed of three fatty acid units linked to glycerol and found in fats and oils.        
    triple bonds Three pairs of electrons being shared by two atoms in a molecule.        
    unit The scale of measurement for a quantity.        
    unsaturated A solution whose solute is less than its solubility limit.        
    unsaturated hydrocarbons An alkene or alkyne having one or more multiple (double or triple) bonds between carbon atoms.        
    valence shell electron pair repulsion, VSEPR The general concept that estimates the shape of a simple molecule.        
    vapor pressure The pressure of a vapor that is in equilibrium with its liquid phase.        
    vapor pressure depression The lowering of the vapor pressure of a solution versus the pure solvent.        
    Viruses An infectious agent that is much smaller and simpler than bacteria.        
    vitamins An organic compound that is essential in very small amounts for the maintenance of normal metabolism.        
    volume The amount of space that a given substance occupies.        
    volume/volume percent A concentration unit that relates the volume of the solute to the volume of the solution.        
    weak base A base that is less than 100% ionized in aqueous solution.        
    zwitterion An electrically neutral compound that contains both negatively and positively charged groups.        
    β-oxidation A sequence of four reactions in which fatty acyl-CoA molecules are oxidized, leading to the removal of acetyl-CoA molecules.        
    • Was this article helpful?